The present invention relates to composite elements constructed from an outer layer (i) and a fiber-reinforced polyurethane (PU) foam with in-mold release additives as supporting layer (ii), and optionally, a decorative inner layer (iii). This invention also relates to suitable processes for the production of these composite elements, and to body components comprising these composite elements.
EP-A-995 667 and EP-A-1 077 225 describe the production of composite components that are constructed from a pigmented, thermoplastic film which is foam-backed with glass fiber-reinforced polyurethane. To produce the colored components, release agents are used for demolding from the modular mold. The composite components are used, for example, as roof modules in motor vehicles.
Furthermore, DE-A 10 160 374 describes a composite part with long glass fiber reinforcement, produced by the LFI (long fiber injection) PU process. In order to remove the part easily from the modular mold, release agents must be applied to the surface of the mold.
For reasons of fast, productive manufacture, it is desirable to avoid the use of external mold release agents. External mold release agents typically require additional spraying, evaporation and drying of the release agent in the mold, and subsequent removal of the release agent from the surfaces of the composite part before lamination or bonding of these components.
The object of the invention was to produce composite elements having excellent mechanical properties and good surface qualities, in which the composite element comprised an outer layer (i) and a supporting layer adhered the outer layer and which comprised fiber-reinforced polyurethane (ii), and optionally, a decorative layer adhered to this supporting layer as an inner layer (iii), wherein the composite elements are formed or produced in such a way that there is no need to use an external mold release agent.
It has now been found that, certain PU formulations which contain specific in-mold release additives can be used in these composite elements. These particular PU formulations provide a very good release behavior from the modular molds, and a very good adhesive bond to all composite layers, i.e. the outer layer (i), the fiber-reinforced polyurethane layer (ii), and, when present, the decorative layer (iii), and additionally, good adhesive bonds to any strengthening and reinforcing elements that are present can also be achieved.